Filtration systems for chemical fluids

ABSTRACT

A method of producing a filtration system for filtering a chemical fluid used in a hydrocarbon extraction well is provided. The method comprises providing a filter arrangement comprising an inlet end and an outlet end, connecting the inlet end to a first fluid flow passageway using a first hydraulically operated connector, and connecting the outlet end to a second fluid flow passageway using a second hydraulically operated connector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to filtration systems forchemical fluids, in particular chemical fluids used in hydrocarbonextraction wells.

2. Description of the Prior Art

Flow lines and pipelines carrying hydrocarbons are subject to build-upof hydrates (which are crystalline in nature) which impede and may blockthe flow of hydrocarbons if not prevented or reduced. It is standardpractice to inject mono ethylene glycol (MEG), which is a hydrateinhibitor, into such flow lines and pipelines for the prevention ofhydrate formation and for the absorption of moisture. This process isnormally carried out, in downtime, when production hydrocarbon fluid isnot passing through the flow line or pipeline concerned. In offshoresubsea control systems, the MEG is typically injected into an umbilicaltopside before being distributed through the subsea control system viaMEG injection valves which are mounted on a suitable host structuresubsea, such as one on a manifold or a Christmas tree or on the seabed,which host structure could be semi-permanent in that it is retrievable.A MEG filtration system comprising a filter module is inserted in theflow line or pipeline immediately before the MEG injection valves toclean the MEG before injection.

This filter module is required because the MEG fluid is retrieved, afteruse and recycled in a recycling plant installed topside to remove thehydrates, pollutants from the well and water. The filter module collectscontaminants suspended in the MEG and protects the inner surfaces ofsubsea MEG injection equipment from mechanical abrasion, resulting inexpected improvement in equipment reliability and longevity. The modulewill require changing at intervals and therefore a method is needed ofachieving this without the loss of MEG, risk of pollution and ingress ofsea water.

As the MEG filter module is mounted on the host structure subsea, aremote method using an ROV is required to remove and re-install thefilter module when required. As shown in FIG. 1, a typical ROVretrievable MEG filter module has a filter arrangement comprising aspool with one or more in-line filters 1 arranged in a 180 degree loop,the arrangement extending from an inlet end 2 to an apex region 3 andback to an outlet end 4. ROV actuated mechanically clamped connectors 5and 6 respectively connect the inlet 2 and the outlet 4 to endconnectors 7 and 8 of a MEG input passageway 9 and a MEG outputpassageway 10 which are mounted on a host structure 11, such as one on apipeline end manifold (PLEM) or a Christmas tree. Isolation valves areplaced both upstream of inlet end 2 and downstream of outlet end 4 inorder to isolate the MEG flow to allow filter module replacement. Oncethe new filter module is latched in place, the isolation valves arereturned to their open positions to re-commence the flow of MEG. Each ofthe connectors 5 and 6 requires an ROV to actuate its mechanical clampsand to disconnect it by rotating a clamp actuating mechanism 12 in orderto remove or reinstall the filter module—see FIG. 1 a which is a planview of one of the connectors showing its clamps 13. Furthermore, themethod of mounting the current filter module in a horizontalconfiguration severely restricts the access for an ROV. Thus the currentprocess of MEG filter replacement is difficult, time consuming andtherefore expensive.

BRIEF SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is provided amethod of producing a filtration system for filtering a chemical fluidused in a hydrocarbon extraction well. The method comprises providing afilter arrangement comprising an inlet end and an outlet end, connectingthe inlet end to a first fluid flow passageway for the fluid using afirst hydraulically operated connector, and connecting the outlet end toa second fluid flow passageway using a second hydraulically operatedconnector.

According to another embodiment of the present invention, there isprovided a method of producing a filtration system for filtering achemical fluid used in a subsea hydrocarbon extraction well. The methodcomprises providing a filter arrangement, and connecting opposite endsof the filter arrangement to respective fluid flow passageways byhydraulically operated connectors using a remotely operated vehiclewhich operates the connectors in a hot stab manner.

According to another embodiment of the present invention, there isprovided a filtration system for filtering a chemical fluid used in ahydrocarbon extraction well. The system comprises a filter arrangementcomprising an inlet end and an outlet end, the inlet end being connectedto a first fluid flow passageway by a first hydraulically operatedconnector, and the outlet end being connected to a second fluid flowpassageway by a second hydraulically operated connector.

Embodiments of the present invention also provide a hydrocarbonextraction well including a filtration system according to otherembodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1 shows a known form of filtration system;

FIG. 1 a shows part of is the filtration system shown in FIG. 1; and

FIG. 2 shows a filtration system according to an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 (in which items which correspond with items in FIG. 1 have thesame reference numerals as in FIG. 1) illustrates an application of anembodiment of the present invention which includes the introduction ofannulus flowline hydraulically operated connectors 14 and 15 to replaceconnectors 5 and 6. Each of connectors 14 and 15 is, by way of example,a Vetco Gray 2 1/16″ flowline hydraulic connector part number A110312-9,to connect the MEG filter arrangement to the semi-permanentinfrastructure. These connectors require hydraulic actuation, which isvia hydraulic pipes 16 and 17 respectively, connected to a verticallymounted ROV hot stab connector portion 18 at the top of the 180 degreeloop, that is on the apex region 3 of the filter arrangement. Thehydraulic connectors 14 and 15 are self-sealing, thus preventing theingress of seawater and the expulsion of MEG during filter arrangementchange. Each connector has a latch mechanism which is hydraulicallydriven open and closed by the supply from the ROV hot stab on twoseparate circuits. A mechanism is engaged on the close stroke whichmechanically latches the connector and the respective one of connectors7 and 8 together. This means, should a hydraulic leak occur on the latchcircuit, the connector will not de-latch. The system remains in stasiswhen the ROV hot stab is removed and until it is hydraulically drivenopen. The connectors 14 and 15 are latched to the end connectors 7 and8, in each case by an annular piston within the connector body movingdownwards, forcing a locking ring radially inwards by means of a surfacemachined on the internal diameter of the piston. Each locking ring mateswith a machined profile on the respective one of end connectors 7 and 8,maintaining sufficient force to maintain the loading of a sealinggasket. The hot stab hydraulic circuit is capable of actuating bothconnectors 14 and 15 simultaneously. A manual over-ride is provided (notshown) should the hydraulic actuation fail whereby the ROV canmechanically separate the two parts of each hot stab connection.

According to an embodiment of the present invention, the filtrationsystem is on a subsea structure. In this case, typically, the connectorsare hydraulically operated by a remotely operated vehicle (ROV). The ROVcauses hydraulic fluid to be supplied to operate said connectors viarespective lines from a connector portion with which the ROV engages.According to an embodiment of the present invention, the ROV engages theconnector portion in a hot stab manner.

According to an embodiment of the present invention, the filterarrangement extends from the inlet end to an apex region and from theapex region to the outlet end. According to an embodiment of the presentinvention, a connector portion is provided at the apex region.

An embodiment of the present invention replaces the mechanically clampedconnectors of a MEG filter module with field proven, hydraulicallyoperated connectors operated by ROV hydraulic power by a hot stabhydraulic connection, thus enabling a quick connect/disconnectcapability.

Subsea hot stab connectors, which are high pressure operated, aredesigned to be ROV operated. One part of such a connector, in anembodiment of the present invention, is attached to the filterarrangement and the ROV inserts another part into the connector so thathigh pressure hydraulic fluid is supplied to operate the hydraulicallyoperated connectors.

The main advantages of using the hot stab operated hydraulic connectorsare improved flexibility for ROV access, reduced time for removal andreplacement of filters, less risk of environmental pollution and seawater ingress, reduction in cost of filter exchange, and use of provenhydraulic connection technology.

1. A method of producing a filtration system for filtering a chemical fluid used in a hydrocarbon extraction well, the method comprising: providing a filter arrangement comprising an inlet end and an outlet end; connecting the inlet end to a first fluid flow passageway using a first hydraulically operated connector; and connecting the outlet end to a second fluid flow passageway using a second hydraulically operated connector.
 2. The method according to claim 1, wherein the well is a subsea well, the filtration system being on a subsea structure.
 3. The method according to claim 2, wherein the connectors are hydraulically operated by a remotely operated vehicle.
 4. The method according to claim 3, wherein the remotely operated vehicle causes hydraulic fluid to be supplied to operate the connectors via respective lines from a connector portion with which the remotely operated vehicle engages.
 5. The method according to claim 4, wherein the remotely operated vehicle engages the connector portion in a hot stab manner.
 6. The method according to claim 1, wherein the filter arrangement further comprises an apex region, wherein the filter arrangement extends from the inlet end to the apex region and from the apex region to the outlet end.
 7. The method according to claim 3, wherein the filter arrangement further comprises an apex region, wherein the filter arrangement extends from the inlet end to the apex region and from the apex region to the outlet end, and wherein the connector portion is at the apex region.
 8. The method according to claim 7, wherein the remotely operated vehicle engages the connector portion in a hot stab manner.
 9. A method of producing a filtration system for filtering a chemical fluid used in a subsea hydrocarbon extraction well, the method comprising: providing a filter arrangement; and connecting opposite ends of the filter arrangement to respective fluid flow passageways by hydraulically operated connectors using a remotely operated vehicle which operates the connectors in a hot stab manner.
 10. The method according to claim 9, wherein the remotely operated vehicle causes hydraulic fluid to be supplied to operate the connectors via respective lines from a connector portion with which the remotely operated vehicle engages.
 11. The method according to claim 9, wherein the filter arrangement comprises an apex region, wherein the filter arrangement extends between the ends via the apex region.
 12. The method according to claim 10, wherein the filter arrangement comprises an apex region, wherein the filter arrangement extends between the ends via an apex region, and wherein the connector portion is at the apex region.
 13. A filtration system for filtering a chemical fluid used in a hydrocarbon extraction well, the system comprising a filter arrangement comprising an inlet end and an outlet end, the inlet end being connected to a first fluid flow passageway by a first hydraulically operated connector, and the outlet end being connected to a second fluid flow passageway by a second hydraulically operated connector.
 14. The system according to claim 13, wherein the filtration system is on a subsea structure of a subsea hydrocarbon extraction well.
 15. The system according to claim 13, wherein the filtration arrangement further comprises an apex region, wherein the filter arrangement extends from the inlet end to the apex region and from the apex region to the outlet end.
 16. The filtration system according to claim 15, wherein the filter arrangement further comprises a connector portion at the apex region, the connector being configured to engage an remotely operated vehicle for hydraulic operation of the connectors.
 17. A hydrocarbon extraction well comprising the filtration system according to claim
 13. 18. A hydrocarbon extraction well comprising the filtration system according to claim
 14. 19. A hydrocarbon extraction well comprising the filtration system according to claim
 15. 20. A hydrocarbon extraction well comprising the filtration system according to claim
 16. 